Hi
I'm not sure I quite understand your post. When a person becomes a a Christian the Holy Spirit immediately writes the good and Holy laws of God on the converts heart and mind, meaning they in their hearts want to obey, their hearts have been softened as Ezekiel prophesied would happen(Ezekiel36:26&27) therefore a person, instinctinctively from the moment of conversion knows how God wants them to live and this is what their heart desires. Therefore, as they want to live as God would have them live, their job is to look to Christ and trust him, that they might recieve through the sanctification of the Spirit an ever more, holy and closer walk with the Lord.
Wait, are you saying that conversion makes people immediately know right from wrong in every situations by direct providence and thus will have no further need to study Gods Law or seek his ways?
What you're proposing doesn't mesh well with reality or scripture... What you're saying sounds a lot more like 'every man doing what is right in their own eyes' than 'one in whom the righteousness of the law is revealed'.
But I will try to re-hash it more concisely.
First off, what Law's do you think the Holy spirit writes on the heart of his Faithfull? Is there some other law you think is written? Some strange law that no one but they know?
Heaven forbid...
Jer 31:31 Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah:
Jer 31:32 Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD:
Jer 31:33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
The old covenant was broken, a new one written, but there is only one Law. The law that the Spirit of God places on ones inward parts is the same law that was on ink and paper, received differently. It is not against us, convicting us, because we are new and forgiven, it is part of us edifying us that we may know how to walk closer to God.
But lets use your own words to help you understand, you had said "
their job is to look to Christ and trust him"
So what did he say on the matter?
Mat 5:19 Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven.
Mat 19:17 And he said unto him, Why callest thou me good? there is none good but one, that is, God: but if thou wilt enter into life, keep the commandments.
Joh 14:15 If ye love me, keep my commandments.
Joh 14:21 He that hath my commandments, and keepeth them, he it is that loveth me: and he that loveth me shall be loved of my Father, and I will love him, and will manifest myself to him.
Joh 15:10 If ye keep my commandments, ye shall abide in my love; even as I have kept my Father's commandments, and abide in his love.
If you love Him, keep His commandments. Who is He? He is God. What commands did God give?
And there we have it.
Understand that one of the biggest things Jesus wants you to do, is keep his commands and teach others to keep them. He didn't come to tear down His own Law, but fully preach and establish it, that is what fulfil means in that chapter.